o Add io trails notebook

Author: rajeeja

io_trials/Agenda

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+Agenda:
+
+1. Design?
+
+2. Work distribution
+
+3. Documentation and coding practices
+
+4. Implementation as per API Document
+
+
+5. Overall goal and success defining criterion?
+
+- read the structured/unstructured File
+- extract data, visualize and do math
+
+6. How would real world applications using uxarray look like?
+
+7.

io_trials/doctest.py

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+import xarray as xr
+import numpy as np
+ds = xr.Dataset()
+ds["mesh2d"] = xr.DataArray(
+    data=0,
+    attrs={
+     "cf_role": "mesh_topology",
+     "long_name": "Topology data of 2D mesh",
+     "topology_dimension": 2,
+     "node_coordinates": "node_x node_y",
+     "face_node_connectivity": "face_nodes",
+    }
+)
+ds = ds.assign_coords(
+    node_x=xr.DataArray(
+        data=np.array([0.0, 10.0, 10.0, 0.0, 20.0, 20.0]),
+        dims=["node"],
+    )
+)
+ds = ds.assign_coords(
+    node_y=xr.DataArray(
+        data=np.array([0.0, 0.0, 10.0, 10.0, 0.0, 10.0]),
+        dims=["node"],
+    )
+)
+ds["face_nodes"] = xr.DataArray(
+    data=np.array([
+        [0, 1, 2, 3],
+        [1, 4, 5, -1]
+    ]),
+    coords={
+        "face_x": ("face", np.array([5.0, 15.0])),
+        "face_y": ("face", np.array([5.0, 5.0])),
+    },
+    dims=["face", "nmax_face"],
+    attrs={
+        "cf_role": "face_node_connectivity",
+        "long_name": "Vertex nodes of mesh faces (counterclockwise)",
+        "start_index": 0,
+        "_FillValue": -1,
+    }
+)
+
+print(ds)
+